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Texture evolution of annealed Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel
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Procedia Manufacturing 15 (2018) 1619–1625 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
17th International Conference on Metal Forming, Metal Forming 2018, 16-19 September 2018, 17th International Conference on MetalToyohashi, Forming, Metal Japan Forming 2018, 16-19 September 2018, Toyohashi, Japan
Texture evolution of annealed Fe-19Cr-2Mo-Nb-Ti ferritic stainless Texture evolution of annealed Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel Conference 2017, MESIC Manufacturing Engineering Society International 2017, 28-30 June steel 2017, Vigo (Pontevedra), Spain Guojun Cai, Changsheng Li*, Dongge Wang, Yongkang Zhou Guojun Cai, Changsheng Li*, Dongge Wang, Yongkang Zhou
State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China Trade-off Costing models for capacity optimization in Industry 4.0: State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China between used capacity and operational efficiency
Abstract Abstract a a,* b A. Santana , P.stainless Afonso A.investigated Zaninb, R. Wernke Texture evolution of Fe-19Cr-2Mo-Nb-Ti ferritic steel ,was under different annealing temperatures. After Texture evolution of Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel was nucleation investigatedsites under different annealing temperatures. cold rolling, the in-grain shear bands provide more recrystallization to {111} recrystallization grains withAfter high a University of Minho, 4800-058 Guimarães, Portugal cold rolling, in-grain shear bands provide more recrystallization nucleation sites the to {111} recrystallization grainsgrains with high Taylor factortheduring recrystallization. AsbUnochapecó, the annealing temperatures increase, average size of annealed and 89809-000 Chapecó, SC, Brazil Taylor factor during increase, recrystallization. the annealing the average size of{111} annealed grains and precipitates gradually and 1050 As °C annealed grains temperatures are dominatedincrease, by the uniform and equiaxial recrystallization precipitates gradually and 1050 °C annealedasgrains are dominated by the uniform andthe equiaxial grains favourable for increase, the formability. Accordingly, the annealing temperatures increase, average{111} plasticrecrystallization strain ratio of grains favourable for the formability. Accordingly, as the annealing temperatures increase, the average plastic strain ratio of annealed sheets rises to 1.71 monotonically. annealed sheets rises to 1.71 monotonically. Abstract © 2018 The Authors. Published by Elsevier B.V. © 2018 2018 The The Authors. Published by Elsevier B.V. © Authors. Published by B.V. Peer-review responsibility of Elsevier the4.0", scientific committee ofthe the17th 17thwill International Conference onMetal MetalForming. Forming. Under the under concept of "Industry production processes be pushed to be on increasingly interconnected, Peer-review under responsibility of the scientific committee of International Conference Peer-review under responsibility of the scientific committee of much the 17thmore International on Metalcapacity Forming.optimization information based on a real time basis and, necessarily, efficient.Conference In this context,
Keywords: Ferritic steel; aim Annealing temperature; Texture; Shearcontributing band; Plastic strain goes beyond thestainless traditional of capacity maximization, also ratio for organization’s profitability and value. Keywords: Ferritic stainless steel; Annealing temperature; Texture; Shear band; Plastic strain ratio Indeed, lean management and continuous improvement approaches suggest capacity optimization instead of maximization. The study of capacity optimization and costing models is an important research topic that deserves 1. Introduction contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical 1. Introduction model for capacity management based on different costing models (ABC and TDABC). A generic model has been Recently, to replace the austenitic stainless steels in most environments, some modified low cost ferritic stainless developed andtoit replace was used analyze idle capacity andin to most design strategies towards maximization offerritic organization’s Recently, thetoaustenitic environments, somethe modified low cost stainless steels have been developed by addingstainless Mo andsteels lowering C and N. Fe-19Cr-2Mo-Nb-Ti ferritic stainless steels with value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown thatsteels capacity steels have been developed by adding Mo and lowering C and N. Fe-19Cr-2Mo-Nb-Ti ferritic stainless higher Cr addition have been used in auto vent pipe which requires excellent corrosion-resistance and formabilitywith [1]. optimization might have hide been operational higher Cr addition used ininefficiency. auto vent pipe which requires excellent [1]. In consideration of temperature oxidation resistance and thermal fatigue life, corrosion-resistance the relatively high Tiand andformability Nb additions © 2017 The Authors. Published by Elsevier B.V. In consideration of temperature oxidation resistance and thermal fatigue life, the relatively high Ti and Nb additions lead to a less stable microstructure susceptible to some intermetallic compounds and carbonitrides, such as Laves Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference lead to aand less(Nb,Ti) stable microstructure susceptible some intermetallic compounds ferritic and carbonitrides, such faces as Laves phases (C,N) precipitates [2, 3].toHowever, Fe-19Cr-2Mo-Nb-Ti stainless steel the 2017. phases and (Nb,Ti) (C,N) precipitates [2, 3]. However, Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel faces the challenge of the lower formability in contrast to austenitic stainless steels, which restricts its application in some challenge of the lower formability in contrast to austenitic stainless steels, which restricts its application in some Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency
1. Introduction
* Corresponding author. Tel.: +86-139-9837-6578; fax: 024-23906472. * E-mail Corresponding Tel.: +86-139-9837-6578; fax: 024-23906472. address:author. [email protected] The cost of idle capacity is a fundamental information for companies and their management of extreme importance E-mail address: [email protected]
in modern©production systems. In general, it isB.V. defined as unused capacity or production potential and can be measured 2351-9789 2018 The Authors. Published by Elsevier 2351-9789 2018 Authors. Published Elsevier B.V.hours of the Peer-review underThe responsibility of theby scientific committee 17th International on Metal Forming. in several©ways: tons of production, available manufacturing, etc.Conference The management of the idle capacity Peer-review under responsibility thefax: scientific committee * Paulo Afonso. Tel.: +351 253 510of 761; +351 253 604 741 of the 17th International Conference on Metal Forming. E-mail address: [email protected]
2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming. 10.1016/j.promfg.2018.07.295
Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
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fields. It has been reported that the formability of FSSs can be improved by r-values strongly linked with the texture evolution, depending on the orientation uniformity and intensity of {111} recrystallization texture [4]. Thus the evolution of textures during annealing can be understood in a better way to find the optimum combination for improving the formability of stainless steel. For this reason, Huh and Engler [5] investigated that the formability of steel improved by the more desirable {111} recrystallization texture could cause a marked increase in the r-values. Ray et al. [6] proposed that low carbon and extra low carbon steels with the high formability could be improved by increasing the r-values, associated with the {111} recrystallization texture. Yan et al. [7] pointed out that the uniform and sharp {111} recrystallization texture was closely related to the uniformity of grain size distribution and the fraction of coincidence site lattice, which obtained higher r-values. Shu et al. [8] suggested that 15%Cr ferritic stainless steel with Ti and Nb additions obtained higher r-values, which were attributed to the high intensity and uniform {111}<112> and{111}<110> components. As such, the careful and overall work is to explain different annealing temperatures and obtain further knowledge about formability of Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel by means of the texture evolution. 2. Materials and experimental procedures 2.1. Test materials In this investigation, Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel with chemical compositions given in Table 1 was made in the high frequency vacuum induction furnace. Table 1. Compositions of experimental steel (wt.%). C 0.009
Si 0.52
Mn 0.32
P 0.008
S 0.008
Cr 19.5
Nb 0.45
Ti 0.155
N 0.072
Mo 1.97
Fe Bal.
2.2. Experimental procedures After forged into 50 mm sheet at 1050-850 °C, it was hot rolled to a 3 mm thick strip by seven passes from 1150 °C to 850 °C on a Φ 450 mm hot rolling mill, then annealed at 1050 °C for 5 min. After annealing in a Nitrogen atmosphere, it was cold rolled to 1 mm in thickness by five passes. The temperatures of final annealing were 850, 950 and 1050 °C, held for 5 min and cooled to room temperature in the air. The microstructure of cold-rolled sample along the longitudinal section as defined by the rolling direction and normal direction was obtained by etching in a solution of 4g CuSO4+30 mL HCl+25 mL H2O, studied using an FEI Quanta 600 scanning electron microscope equipped with an OIM 4000 electron backscatter diffraction detector, and the orientation distribution functions had been measured and calculated in the center layer based on X-ray diffraction. The average r-values were measured using SANS CMT7000 universal testing machine, and machined at angles of 0º ( r 0 ), 45º( r 45 ) and 90º ( r 90 ) to the rolling direction. 3. Results and discussion 3.1. Hot-rolled sheet and cold-rolled sheet Fig. 1 reveals the orientation image map of hot-rolled sheet and annealed sheets. There are some elongated grains with continuous {100} orientation comprising the rotating cube orientation {100}<011> and cube orientation {100}<001>in the center area, as well as a little indistinctive Goss-oriented grains and deformed {111} orientation grains on the surface layer (Fig. 1a). Goss-oriented grains are nucleated mainly within or around the deformed elongate grains with the {111} orientation during hot rolling under the shear stress. The annealed sheet is composed of uniform and equiaxial recrystallization grains of 50-70 μm in size, and the texture is characterized by strong {111}
Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
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recrystallization texture (Fig. 1b) because the deformation grains with the {100} orientation in the hot-rolled sheet are changed into the {111} recrystallization grains. (a)
ND RD
(b)
200µm
ND RD
100µm
Fig. 1. Orientation image map of (a) hot-rolled sheet and (b) annealed sheet.
Fig. 2 presents the microstructures and orientation image map of cold-rolled sheet. It is clearly that after cold rolling, the grains containing some in-grain shear bands are inclined at angles of 30º to rolling direction, and these shear bands are preferential sites for the nucleation of new γ-fiber grains which will be nucleated and grow prior to those having other orientations during annealing (Fig. 2(a)). A large number of recrystallization grains with {111}<110> and {111}<112> textures occur on in-grain shear bands with the {100} orientation due to the dynamic recrystallization and high stored energy (Fig. 2(b)). (b)
(a)
ND RD
100µm
ND RD
50µm
Fig. 2. (a) Microstructure and (b) orientation image map of cold-rolled sheet.
As an ultra-low carbon steel, Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel with high stacking fault energy remains in ferrite phase throughout the entire processing route. A remarkably inhomogeneous microstructure resulting from the recovery and partial recrystallization is attributed to the work hardening difference among the deformation grains with various orientations. Some finer recrystallization grains will form on the surface of hot-rolled sheet because of the increased internal stored energy when the plastic deformation increases and occurs in each pass during hot rolling. After the stored energy is accumulated to a certain degree, as a driving force for the recovery and recrystallization, an increase in the stored energy is conducive to the dynamic recrystallization phenomenon, which is the case with a little indistinctive deformed grains with the {111} orientation identified as the higher Taylor factor on the surface layer [9]. Thus far, it is known that the stored energy and mobility are intrinsic factors that cause recrystallization behavior and grain growth, and the texture is external factor whose intensity determines whether the recrystallization grain growth appears [10]. Based on the oriented nucleation selective growth mechanism, the recrystallization grains
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Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
are nucleated mainly the original grain boundaries, and the nuclei in local regions with the highest stored energy grow up during annealing. Generally, the nucleation and growth rate of the recrystallization grains are determined by various deformation stored energy in each grain (viz. Taylor factors) [11]. Depending on Taylor factors of recrystallization textures, the degree of Goss texture is dependent upon the accurate {110}<001> nucleus and the strong {111}<112> orientation in primary recrystallization texture. After hot rolling, γ-fiber recrystallization texture with the higher Taylor factor first nucleates in the matrix, and the {111}<112> and{111}<110> recrystallization grains are swallowed by the {110}<001> Goss-oriented grains endowed with the lower Taylor factor, and then the deformation textures mainly concentrate on the {110}<001> Goss texture, {100}<001> and {100}<011> components, accompanying with the lower and dispersed {111}<110> and {111}<112> textures. Jonas [12] pointed out that the shear bands of cold-rolled sheet stimulated the nucleation of γ-fiber recrystallized grains by reducing the number of α-fiber grains, and provided more recrystallization nucleation sites to grains with high Taylor factor orientations, such as {111}<110> and {111}<112> components, which enhanced the formation of {111} textures in grain interiors during recrystallization. In addition, the shear bands exhibiting various orientations due to localized plastic flows as compared to the matrix, can influence the texture evolution routes and provide more nucleation sites for recrystallization, and prevent the matrix rotating from {110}<001> Goss texture to the {223} <110> texture during cold rolling [13]. 3.2. Final annealed sheets In order to clearly demonstrate the evolution of texture, Fig. 3 reveals the Orientation image maps and orientation distribution functions of sheets with different annealing temperatures, and the orientation maps present the crystalline directions parallel to rolling direction as indicated by the colors in the stereographic triangle. It is clearly that 850 °C annealed sheet has weak {101} texture component, strong {111} and {001} texture components, and some elongated grains with continuous {100} orientation comprising the {100}<001> cube orientation and {100}<011> rotating cube orientation. After annealing at 950 °C, the smaller grains with average size of ~12 μm possessed low stored energy are observed, consumed by the pre-existing recrystallized grains because of a low driving force for nucleation (Fig. 3(c)). In contrast, most grains in the 1050 °C annealed sheet are equiaxed grains with average size of ~50 μm originated from the {001} deformed grains. Meanwhile, the annealed grains are dominated by massive uniform and equiaxial γ-fiber recrystallization grains (the {111}<110> and {111}<112> components) favourable for the improvement of r-values, and the {111}<110> and {111}<112> components account for 33.4% and 50.7%, respectively (Fig. 3(e)). Fig. 4 presents the macro-textures in center layer of annealed sheets. Macro-textures of 850 °C annealed sheets are mainly composed of uneven α-fiber ({110} orientation) texture and γ-fiber recrystallization texture, as well as the weak rotating cube orientation {100}<110 > texture (Fig. 4a). With increasing the annealing temperatures, the stored energy will be released and the sites of recrystallization nucleation in the annealed sheet are on the increase, which leads to the improvement of recrystallization nucleation rate and the development of γ-fiber texture. After annealing at 950 °C, the density of α-fiber texture is weakened and the whole intensity of γ-fiber texture is significantly enhanced, and its textures are dominated by the {111}<112> and {111}<110> components (Fig. 4(b)). When the annealing temperature reaches 1050 °C, γ-fiber recrystallization texture is on the increase, and the intensity of {111}<112> texture is changed from 8.92 to 11.45 with the growth of recrystallization grains, as shown in Fig. 4(c).
Author name / Procedia Manufacturing 00 (2018) 000–000 Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625
(a)
ND RD
(b)
200µm
(c)
ND RD
5 1623
(d)
200µm (f)
(e)
ND RD
200µm
Fig. 3. Orientation image maps and orientation distribution functions of final annealed sheets: (a,b) 850 °C for 5 min; (c,d) 950 °C for 5 min and (e,f) 1050 °C for 5 min.
Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
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(a)
(c)
(b)
Fig. 4. Macro-textures (φ2 =45° section of the ODFs) in center layer of annealed sheets: (a) 850 °C for 5 min; (b) 950 °C for 5 min and (c) 1050 °C for 5 min.
With respect to stored energy and nucleation, the metastable {110}<001> orientation will rotate along the following path: {110}<001>→{001}<110>→{554}<225>→{111}<112>→{111}<110> [14]. During annealing, the {111}<110> recrystallization grains will form nucleus and grow in the deformation matrix containing the {111}<112> orientation [15], as well as the recrystallization grains with the {111}<112> orientation will form nucleus and grow in the {111}<110> matrix by means of the migration of Σ13b CSL boundaries which is quite close to the ideal orientation relationship between {111}<112> and{111}<110> orientations (30º<111>). Accompanied with an increase in the annealing temperature, the metastable {110}<001> orientation is gradually turned into more stable {001}<110> texture (Fig. 5(a)), finally transformed into γ-fiber texture comprising the {111}<110> and {111}<112> components conducive to the formability (Fig. 5(c)). 3.3. Formability Depending on the tensile tests, the average plastic strain ratio ( r ) evaluating the degree of tensile deformation and the quality of products can be calculated by: r=
r0 + r90 + 2r45 . 4
(1)
Table 2 displays the values of final sheets under different annealing processes. It is apparent from Table 2 that with increased the annealing temperatures, the r values of final annealed sheets increase monotonically. In BCC iron, the {111}<110> and {111}<112> components are beneficial to the formability [16]. With increasing the annealing temperatures, the α-fiber texture is weakened and the whole intensities of {111}<110> and {111}<112> components belonging to γ-fiber recrystallization texture are significantly improved, which is favourable for the increase of r value. Table 2. Average plastic strain ratio of final sheets under different annealing processes. Annealing processes
r0
r45
r90
850 °C for 5 min 950 °C for 5 min 1050 °C for 5 min
1.48 1.71 1.97
1.08 1.22 1.59
1.24 1.37 1.69
r
1.22 1.38 1.71
4. Conclusions In the present work, the texture evolution of Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel has been investigated under different annealing temperatures. After cold rolling, the in-grain shear bands provide more recrystallization nucleation sites to grains with high Taylor factor orientations, such as {111}<110> and {111}<112> textures. With the increase of annealing temperatures, and 1050 °C annealed grains are dominated by the uniform and equiaxial
Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
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{111} recrystallization grains favourable for the improvement of r-values, which obtains an increase in the average plastic strain ratio and excellent formability of final sheets. Acknowledgements This work was supported by the National Natural Science Foundation of China and Baowu Steel Group Co. Ltd (Grant No. U1660205). References [1] T. Juuti, L. Rovatti, A. Mäkelä, L.P. Karjalainen, D. Porter, Influence of long heat treatments on the laves phase nucleation in a type 444 ferritic stainless steel, Journal of Alloys and Compounds, 616 (2014) 250–256. [2] B.S.S. Prasad, V.B. Rajkumar, K.C.H. Kumar, Numerical simulation of precipitate evolution in ferritic–martensitic powerplant steels, CALPHAD: Computer Coupling of Phase Diagrams and Thermochemistry, 36 (2012) 1–7. [3] J. Kim, J.G. Jung, D.H. Kim, Y.K. Lee, The kinetics of Nb(C,N) precipitation during the isothermal austenite to ferrite transformation in a low-carbon Nb-microalloyed steel, Acta Materialia, 61 (2013) 7437–7443. [4] Y.B. Park, D.N. Lee, G. Gottstein, Development of texture inhomogeneity during hot rolling in interstitial free steel, Acta Materialia, 44 (1996) 3421–3427. [5] M.Y. Huh, O. Engler, Effect of intermediate annealing on texture, formability and ridging of 17%Cr ferritic stainless steel sheet, Materials Science & Engineering: A, 308 (2001) 74–87. [6] R.K. Ray, J.J. Jonas, R.E. Hook, Cold rolling and annealing textures in low carbon and extra low carbon steels, International Materials Reviews, 39 (1994) 129–172. [7] H.T. Yan, H.Y. Bi, X. Li, Z. Xu, Effect of two-step cold rolling and annealing on texture, grain boundary character distribution and r-value of Nb + Ti stabilized ferritic stainless steel, Materials Characterization, 60 (2009) 65–68. [8] J. Shu, H.Y. Bi, X. Li, Z. Xu, Effect of Ti addition on forming limit diagrams of Nb-bearing ferritic stainless steel, Journal of Materials Processing Technology, 212 (2012) 59–65. [9] G.J. Cai, C.S. Li, B. Cai, Q.W. Wang, An investigation on the role of texture evolution and ordered phase transition in soft magnetic properties of Fe–6.5 wt%Si electrical steel, Journal of Magnetism and Magnetic Materials, 430 (2017) 70–77. [10] N. Bernier, E. Leunis, C. Furtado, T.V.D. Putte, G. Ban, EBSD study of angular deviations from the Goss component ingrain-oriented electrical steels, Micron, 54-55 (2013) 43–51. [11] X.H. Bian, Y.P. Zeng, D. Nan, M. Wu, The effect of copper precipitates on the recrystallization textures and magnetic properties of nonoriented electrical steels, Journal of Alloys and Compounds, 588 (2014) 108–113. [12] J.J. Jonas, Effects of shear band formation on texture development in warm-rolled IF steels, Journal of Materials Processing Technology, 117 (2001) 293–299. [13] C. Zhang, Z.Y. Liu, G.D. Wang, Effects of hot rolled shear bands on formability and surface ridging of an ultra purified 21%Cr ferritic stainless steel, Journal of Materials Processing Technology, 211 (2011) 1051–1059. [14] J.K. Kim, D.N. Lee, Y.M. Koo, The evolution of the Goss and Cube textures in electrical steel, Materials Letters, 122 (2014) 110–113. [15] P. Ghosh, R.R. Chromik, B. Vashegi, A.M. Knight, Effect of crystallographic texture on the bulk magnetic properties of non-oriented electrical steels, Journal of Magnetism and Magnetic Materials, 365 (2014) 14–22. [16] H.F.G.D. Abreu, A.D.S. Bruno, S.S.M. Tavares, R.P. Santos, S.S. Carvalho, Effect of high temperature annealing on texture and microstructure on an AISI-444 ferritic stainless steel, Materials Characterization, 57 (2006) 342–347.
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Procedia Manufacturing 00 (2018) 000–000 Available online atatwww.sciencedirect.com Available www.sciencedirect.com Procedia online Manufacturing 00 (2018) 000–000
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www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Manufacturing 15 (2018) 1619–1625 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
17th International Conference on Metal Forming, Metal Forming 2018, 16-19 September 2018, 17th International Conference on MetalToyohashi, Forming, Metal Japan Forming 2018, 16-19 September 2018, Toyohashi, Japan
Texture evolution of annealed Fe-19Cr-2Mo-Nb-Ti ferritic stainless Texture evolution of annealed Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel Conference 2017, MESIC Manufacturing Engineering Society International 2017, 28-30 June steel 2017, Vigo (Pontevedra), Spain Guojun Cai, Changsheng Li*, Dongge Wang, Yongkang Zhou Guojun Cai, Changsheng Li*, Dongge Wang, Yongkang Zhou
State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China Trade-off Costing models for capacity optimization in Industry 4.0: State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China between used capacity and operational efficiency
Abstract Abstract a a,* b A. Santana , P.stainless Afonso A.investigated Zaninb, R. Wernke Texture evolution of Fe-19Cr-2Mo-Nb-Ti ferritic steel ,was under different annealing temperatures. After Texture evolution of Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel was nucleation investigatedsites under different annealing temperatures. cold rolling, the in-grain shear bands provide more recrystallization to {111} recrystallization grains withAfter high a University of Minho, 4800-058 Guimarães, Portugal cold rolling, in-grain shear bands provide more recrystallization nucleation sites the to {111} recrystallization grainsgrains with high Taylor factortheduring recrystallization. AsbUnochapecó, the annealing temperatures increase, average size of annealed and 89809-000 Chapecó, SC, Brazil Taylor factor during increase, recrystallization. the annealing the average size of{111} annealed grains and precipitates gradually and 1050 As °C annealed grains temperatures are dominatedincrease, by the uniform and equiaxial recrystallization precipitates gradually and 1050 °C annealedasgrains are dominated by the uniform andthe equiaxial grains favourable for increase, the formability. Accordingly, the annealing temperatures increase, average{111} plasticrecrystallization strain ratio of grains favourable for the formability. Accordingly, as the annealing temperatures increase, the average plastic strain ratio of annealed sheets rises to 1.71 monotonically. annealed sheets rises to 1.71 monotonically. Abstract © 2018 The Authors. Published by Elsevier B.V. © 2018 2018 The The Authors. Published by Elsevier B.V. © Authors. Published by B.V. Peer-review responsibility of Elsevier the4.0", scientific committee ofthe the17th 17thwill International Conference onMetal MetalForming. Forming. Under the under concept of "Industry production processes be pushed to be on increasingly interconnected, Peer-review under responsibility of the scientific committee of International Conference Peer-review under responsibility of the scientific committee of much the 17thmore International on Metalcapacity Forming.optimization information based on a real time basis and, necessarily, efficient.Conference In this context,
Keywords: Ferritic steel; aim Annealing temperature; Texture; Shearcontributing band; Plastic strain goes beyond thestainless traditional of capacity maximization, also ratio for organization’s profitability and value. Keywords: Ferritic stainless steel; Annealing temperature; Texture; Shear band; Plastic strain ratio Indeed, lean management and continuous improvement approaches suggest capacity optimization instead of maximization. The study of capacity optimization and costing models is an important research topic that deserves 1. Introduction contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical 1. Introduction model for capacity management based on different costing models (ABC and TDABC). A generic model has been Recently, to replace the austenitic stainless steels in most environments, some modified low cost ferritic stainless developed andtoit replace was used analyze idle capacity andin to most design strategies towards maximization offerritic organization’s Recently, thetoaustenitic environments, somethe modified low cost stainless steels have been developed by addingstainless Mo andsteels lowering C and N. Fe-19Cr-2Mo-Nb-Ti ferritic stainless steels with value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown thatsteels capacity steels have been developed by adding Mo and lowering C and N. Fe-19Cr-2Mo-Nb-Ti ferritic stainless higher Cr addition have been used in auto vent pipe which requires excellent corrosion-resistance and formabilitywith [1]. optimization might have hide been operational higher Cr addition used ininefficiency. auto vent pipe which requires excellent [1]. In consideration of temperature oxidation resistance and thermal fatigue life, corrosion-resistance the relatively high Tiand andformability Nb additions © 2017 The Authors. Published by Elsevier B.V. In consideration of temperature oxidation resistance and thermal fatigue life, the relatively high Ti and Nb additions lead to a less stable microstructure susceptible to some intermetallic compounds and carbonitrides, such as Laves Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference lead to aand less(Nb,Ti) stable microstructure susceptible some intermetallic compounds ferritic and carbonitrides, such faces as Laves phases (C,N) precipitates [2, 3].toHowever, Fe-19Cr-2Mo-Nb-Ti stainless steel the 2017. phases and (Nb,Ti) (C,N) precipitates [2, 3]. However, Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel faces the challenge of the lower formability in contrast to austenitic stainless steels, which restricts its application in some challenge of the lower formability in contrast to austenitic stainless steels, which restricts its application in some Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency
1. Introduction
* Corresponding author. Tel.: +86-139-9837-6578; fax: 024-23906472. * E-mail Corresponding Tel.: +86-139-9837-6578; fax: 024-23906472. address:author. [email protected] The cost of idle capacity is a fundamental information for companies and their management of extreme importance E-mail address: [email protected]
in modern©production systems. In general, it isB.V. defined as unused capacity or production potential and can be measured 2351-9789 2018 The Authors. Published by Elsevier 2351-9789 2018 Authors. Published Elsevier B.V.hours of the Peer-review underThe responsibility of theby scientific committee 17th International on Metal Forming. in several©ways: tons of production, available manufacturing, etc.Conference The management of the idle capacity Peer-review under responsibility thefax: scientific committee * Paulo Afonso. Tel.: +351 253 510of 761; +351 253 604 741 of the 17th International Conference on Metal Forming. E-mail address: [email protected]
2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming. 10.1016/j.promfg.2018.07.295
Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
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fields. It has been reported that the formability of FSSs can be improved by r-values strongly linked with the texture evolution, depending on the orientation uniformity and intensity of {111} recrystallization texture [4]. Thus the evolution of textures during annealing can be understood in a better way to find the optimum combination for improving the formability of stainless steel. For this reason, Huh and Engler [5] investigated that the formability of steel improved by the more desirable {111} recrystallization texture could cause a marked increase in the r-values. Ray et al. [6] proposed that low carbon and extra low carbon steels with the high formability could be improved by increasing the r-values, associated with the {111} recrystallization texture. Yan et al. [7] pointed out that the uniform and sharp {111} recrystallization texture was closely related to the uniformity of grain size distribution and the fraction of coincidence site lattice, which obtained higher r-values. Shu et al. [8] suggested that 15%Cr ferritic stainless steel with Ti and Nb additions obtained higher r-values, which were attributed to the high intensity and uniform {111}<112> and{111}<110> components. As such, the careful and overall work is to explain different annealing temperatures and obtain further knowledge about formability of Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel by means of the texture evolution. 2. Materials and experimental procedures 2.1. Test materials In this investigation, Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel with chemical compositions given in Table 1 was made in the high frequency vacuum induction furnace. Table 1. Compositions of experimental steel (wt.%). C 0.009
Si 0.52
Mn 0.32
P 0.008
S 0.008
Cr 19.5
Nb 0.45
Ti 0.155
N 0.072
Mo 1.97
Fe Bal.
2.2. Experimental procedures After forged into 50 mm sheet at 1050-850 °C, it was hot rolled to a 3 mm thick strip by seven passes from 1150 °C to 850 °C on a Φ 450 mm hot rolling mill, then annealed at 1050 °C for 5 min. After annealing in a Nitrogen atmosphere, it was cold rolled to 1 mm in thickness by five passes. The temperatures of final annealing were 850, 950 and 1050 °C, held for 5 min and cooled to room temperature in the air. The microstructure of cold-rolled sample along the longitudinal section as defined by the rolling direction and normal direction was obtained by etching in a solution of 4g CuSO4+30 mL HCl+25 mL H2O, studied using an FEI Quanta 600 scanning electron microscope equipped with an OIM 4000 electron backscatter diffraction detector, and the orientation distribution functions had been measured and calculated in the center layer based on X-ray diffraction. The average r-values were measured using SANS CMT7000 universal testing machine, and machined at angles of 0º ( r 0 ), 45º( r 45 ) and 90º ( r 90 ) to the rolling direction. 3. Results and discussion 3.1. Hot-rolled sheet and cold-rolled sheet Fig. 1 reveals the orientation image map of hot-rolled sheet and annealed sheets. There are some elongated grains with continuous {100} orientation comprising the rotating cube orientation {100}<011> and cube orientation {100}<001>in the center area, as well as a little indistinctive Goss-oriented grains and deformed {111} orientation grains on the surface layer (Fig. 1a). Goss-oriented grains are nucleated mainly within or around the deformed elongate grains with the {111} orientation during hot rolling under the shear stress. The annealed sheet is composed of uniform and equiaxial recrystallization grains of 50-70 μm in size, and the texture is characterized by strong {111}
Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
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recrystallization texture (Fig. 1b) because the deformation grains with the {100} orientation in the hot-rolled sheet are changed into the {111} recrystallization grains. (a)
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(b)
200µm
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Fig. 1. Orientation image map of (a) hot-rolled sheet and (b) annealed sheet.
Fig. 2 presents the microstructures and orientation image map of cold-rolled sheet. It is clearly that after cold rolling, the grains containing some in-grain shear bands are inclined at angles of 30º to rolling direction, and these shear bands are preferential sites for the nucleation of new γ-fiber grains which will be nucleated and grow prior to those having other orientations during annealing (Fig. 2(a)). A large number of recrystallization grains with {111}<110> and {111}<112> textures occur on in-grain shear bands with the {100} orientation due to the dynamic recrystallization and high stored energy (Fig. 2(b)). (b)
(a)
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100µm
ND RD
50µm
Fig. 2. (a) Microstructure and (b) orientation image map of cold-rolled sheet.
As an ultra-low carbon steel, Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel with high stacking fault energy remains in ferrite phase throughout the entire processing route. A remarkably inhomogeneous microstructure resulting from the recovery and partial recrystallization is attributed to the work hardening difference among the deformation grains with various orientations. Some finer recrystallization grains will form on the surface of hot-rolled sheet because of the increased internal stored energy when the plastic deformation increases and occurs in each pass during hot rolling. After the stored energy is accumulated to a certain degree, as a driving force for the recovery and recrystallization, an increase in the stored energy is conducive to the dynamic recrystallization phenomenon, which is the case with a little indistinctive deformed grains with the {111} orientation identified as the higher Taylor factor on the surface layer [9]. Thus far, it is known that the stored energy and mobility are intrinsic factors that cause recrystallization behavior and grain growth, and the texture is external factor whose intensity determines whether the recrystallization grain growth appears [10]. Based on the oriented nucleation selective growth mechanism, the recrystallization grains
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Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
are nucleated mainly the original grain boundaries, and the nuclei in local regions with the highest stored energy grow up during annealing. Generally, the nucleation and growth rate of the recrystallization grains are determined by various deformation stored energy in each grain (viz. Taylor factors) [11]. Depending on Taylor factors of recrystallization textures, the degree of Goss texture is dependent upon the accurate {110}<001> nucleus and the strong {111}<112> orientation in primary recrystallization texture. After hot rolling, γ-fiber recrystallization texture with the higher Taylor factor first nucleates in the matrix, and the {111}<112> and{111}<110> recrystallization grains are swallowed by the {110}<001> Goss-oriented grains endowed with the lower Taylor factor, and then the deformation textures mainly concentrate on the {110}<001> Goss texture, {100}<001> and {100}<011> components, accompanying with the lower and dispersed {111}<110> and {111}<112> textures. Jonas [12] pointed out that the shear bands of cold-rolled sheet stimulated the nucleation of γ-fiber recrystallized grains by reducing the number of α-fiber grains, and provided more recrystallization nucleation sites to grains with high Taylor factor orientations, such as {111}<110> and {111}<112> components, which enhanced the formation of {111} textures in grain interiors during recrystallization. In addition, the shear bands exhibiting various orientations due to localized plastic flows as compared to the matrix, can influence the texture evolution routes and provide more nucleation sites for recrystallization, and prevent the matrix rotating from {110}<001> Goss texture to the {223} <110> texture during cold rolling [13]. 3.2. Final annealed sheets In order to clearly demonstrate the evolution of texture, Fig. 3 reveals the Orientation image maps and orientation distribution functions of sheets with different annealing temperatures, and the orientation maps present the crystalline directions parallel to rolling direction as indicated by the colors in the stereographic triangle. It is clearly that 850 °C annealed sheet has weak {101} texture component, strong {111} and {001} texture components, and some elongated grains with continuous {100} orientation comprising the {100}<001> cube orientation and {100}<011> rotating cube orientation. After annealing at 950 °C, the smaller grains with average size of ~12 μm possessed low stored energy are observed, consumed by the pre-existing recrystallized grains because of a low driving force for nucleation (Fig. 3(c)). In contrast, most grains in the 1050 °C annealed sheet are equiaxed grains with average size of ~50 μm originated from the {001} deformed grains. Meanwhile, the annealed grains are dominated by massive uniform and equiaxial γ-fiber recrystallization grains (the {111}<110> and {111}<112> components) favourable for the improvement of r-values, and the {111}<110> and {111}<112> components account for 33.4% and 50.7%, respectively (Fig. 3(e)). Fig. 4 presents the macro-textures in center layer of annealed sheets. Macro-textures of 850 °C annealed sheets are mainly composed of uneven α-fiber ({110} orientation) texture and γ-fiber recrystallization texture, as well as the weak rotating cube orientation {100}<110 > texture (Fig. 4a). With increasing the annealing temperatures, the stored energy will be released and the sites of recrystallization nucleation in the annealed sheet are on the increase, which leads to the improvement of recrystallization nucleation rate and the development of γ-fiber texture. After annealing at 950 °C, the density of α-fiber texture is weakened and the whole intensity of γ-fiber texture is significantly enhanced, and its textures are dominated by the {111}<112> and {111}<110> components (Fig. 4(b)). When the annealing temperature reaches 1050 °C, γ-fiber recrystallization texture is on the increase, and the intensity of {111}<112> texture is changed from 8.92 to 11.45 with the growth of recrystallization grains, as shown in Fig. 4(c).
Author name / Procedia Manufacturing 00 (2018) 000–000 Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625
(a)
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(b)
200µm
(c)
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5 1623
(d)
200µm (f)
(e)
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Fig. 3. Orientation image maps and orientation distribution functions of final annealed sheets: (a,b) 850 °C for 5 min; (c,d) 950 °C for 5 min and (e,f) 1050 °C for 5 min.
Guojun Cai et al. / Procedia Manufacturing 15 (2018) 1619–1625 Author name / Procedia Manufacturing 00 (2018) 000–000
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(a)
(c)
(b)
Fig. 4. Macro-textures (φ2 =45° section of the ODFs) in center layer of annealed sheets: (a) 850 °C for 5 min; (b) 950 °C for 5 min and (c) 1050 °C for 5 min.
With respect to stored energy and nucleation, the metastable {110}<001> orientation will rotate along the following path: {110}<001>→{001}<110>→{554}<225>→{111}<112>→{111}<110> [14]. During annealing, the {111}<110> recrystallization grains will form nucleus and grow in the deformation matrix containing the {111}<112> orientation [15], as well as the recrystallization grains with the {111}<112> orientation will form nucleus and grow in the {111}<110> matrix by means of the migration of Σ13b CSL boundaries which is quite close to the ideal orientation relationship between {111}<112> and{111}<110> orientations (30º<111>). Accompanied with an increase in the annealing temperature, the metastable {110}<001> orientation is gradually turned into more stable {001}<110> texture (Fig. 5(a)), finally transformed into γ-fiber texture comprising the {111}<110> and {111}<112> components conducive to the formability (Fig. 5(c)). 3.3. Formability Depending on the tensile tests, the average plastic strain ratio ( r ) evaluating the degree of tensile deformation and the quality of products can be calculated by: r=
r0 + r90 + 2r45 . 4
(1)
Table 2 displays the values of final sheets under different annealing processes. It is apparent from Table 2 that with increased the annealing temperatures, the r values of final annealed sheets increase monotonically. In BCC iron, the {111}<110> and {111}<112> components are beneficial to the formability [16]. With increasing the annealing temperatures, the α-fiber texture is weakened and the whole intensities of {111}<110> and {111}<112> components belonging to γ-fiber recrystallization texture are significantly improved, which is favourable for the increase of r value. Table 2. Average plastic strain ratio of final sheets under different annealing processes. Annealing processes
r0
r45
r90
850 °C for 5 min 950 °C for 5 min 1050 °C for 5 min
1.48 1.71 1.97
1.08 1.22 1.59
1.24 1.37 1.69
r
1.22 1.38 1.71
4. Conclusions In the present work, the texture evolution of Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel has been investigated under different annealing temperatures. After cold rolling, the in-grain shear bands provide more recrystallization nucleation sites to grains with high Taylor factor orientations, such as {111}<110> and {111}<112> textures. With the increase of annealing temperatures, and 1050 °C annealed grains are dominated by the uniform and equiaxial
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{111} recrystallization grains favourable for the improvement of r-values, which obtains an increase in the average plastic strain ratio and excellent formability of final sheets. Acknowledgements This work was supported by the National Natural Science Foundation of China and Baowu Steel Group Co. Ltd (Grant No. U1660205). References [1] T. Juuti, L. Rovatti, A. Mäkelä, L.P. Karjalainen, D. Porter, Influence of long heat treatments on the laves phase nucleation in a type 444 ferritic stainless steel, Journal of Alloys and Compounds, 616 (2014) 250–256. [2] B.S.S. Prasad, V.B. Rajkumar, K.C.H. Kumar, Numerical simulation of precipitate evolution in ferritic–martensitic powerplant steels, CALPHAD: Computer Coupling of Phase Diagrams and Thermochemistry, 36 (2012) 1–7. [3] J. Kim, J.G. Jung, D.H. Kim, Y.K. Lee, The kinetics of Nb(C,N) precipitation during the isothermal austenite to ferrite transformation in a low-carbon Nb-microalloyed steel, Acta Materialia, 61 (2013) 7437–7443. [4] Y.B. Park, D.N. Lee, G. Gottstein, Development of texture inhomogeneity during hot rolling in interstitial free steel, Acta Materialia, 44 (1996) 3421–3427. [5] M.Y. Huh, O. Engler, Effect of intermediate annealing on texture, formability and ridging of 17%Cr ferritic stainless steel sheet, Materials Science & Engineering: A, 308 (2001) 74–87. [6] R.K. Ray, J.J. Jonas, R.E. Hook, Cold rolling and annealing textures in low carbon and extra low carbon steels, International Materials Reviews, 39 (1994) 129–172. [7] H.T. Yan, H.Y. Bi, X. Li, Z. Xu, Effect of two-step cold rolling and annealing on texture, grain boundary character distribution and r-value of Nb + Ti stabilized ferritic stainless steel, Materials Characterization, 60 (2009) 65–68. [8] J. Shu, H.Y. Bi, X. Li, Z. Xu, Effect of Ti addition on forming limit diagrams of Nb-bearing ferritic stainless steel, Journal of Materials Processing Technology, 212 (2012) 59–65. [9] G.J. Cai, C.S. Li, B. Cai, Q.W. Wang, An investigation on the role of texture evolution and ordered phase transition in soft magnetic properties of Fe–6.5 wt%Si electrical steel, Journal of Magnetism and Magnetic Materials, 430 (2017) 70–77. [10] N. Bernier, E. Leunis, C. Furtado, T.V.D. Putte, G. Ban, EBSD study of angular deviations from the Goss component ingrain-oriented electrical steels, Micron, 54-55 (2013) 43–51. [11] X.H. Bian, Y.P. Zeng, D. Nan, M. Wu, The effect of copper precipitates on the recrystallization textures and magnetic properties of nonoriented electrical steels, Journal of Alloys and Compounds, 588 (2014) 108–113. [12] J.J. Jonas, Effects of shear band formation on texture development in warm-rolled IF steels, Journal of Materials Processing Technology, 117 (2001) 293–299. [13] C. Zhang, Z.Y. Liu, G.D. Wang, Effects of hot rolled shear bands on formability and surface ridging of an ultra purified 21%Cr ferritic stainless steel, Journal of Materials Processing Technology, 211 (2011) 1051–1059. [14] J.K. Kim, D.N. Lee, Y.M. Koo, The evolution of the Goss and Cube textures in electrical steel, Materials Letters, 122 (2014) 110–113. [15] P. Ghosh, R.R. Chromik, B. Vashegi, A.M. Knight, Effect of crystallographic texture on the bulk magnetic properties of non-oriented electrical steels, Journal of Magnetism and Magnetic Materials, 365 (2014) 14–22. [16] H.F.G.D. Abreu, A.D.S. Bruno, S.S.M. Tavares, R.P. Santos, S.S. Carvalho, Effect of high temperature annealing on texture and microstructure on an AISI-444 ferritic stainless steel, Materials Characterization, 57 (2006) 342–347.